Even 10 years after that fateful day in September 2001, most Americans over a certain age can still vividly recall exactly what they were doing when they heard the news: terrorists had hijacked American Airlines Flight 11, en route from Boston to Los Angeles, and crashed the aircraft into the North Tower of the World Trade Center in New York City. Glued to televisions, radios, and the Internet, Americans from coast to coast were caught up in the horror of events as they unfolded over the next several hours. By the time the sun had set on September 11, four planes had been hijacked, the Twin Towers of the World Trade Center had been destroyed, the Pentagon attacked, and a nation was in shock.

Immediately and indelibly, 9/11 became a defining moment in the lives of millions of Americans, just as the Japanese bombing of Pearl Harbor in 1941 or the 1969 moon landing had been for previous generations. And although it has been a part of the national consciousness for a decade, it is a part that many have found difficult to accept. After fear and sorrow came an outpouring of patriotism and a fervent desire to prevent such an attack from happening again. But, as months turned into years, the unity and clarity of purpose that 9/11 initially engendered dissolved in the face of the complexities of its aftermath.

For many, it is difficult to gauge how far the nation has come since 2001. On the one hand, the United States has remained untouched by another terrorist attack of 9/11's magnitude, and in May 2011 U.S. special forces at last located and killed Al Qaeda leader and September 11 mastermind Osama bin Laden. On the other hand, however, thousands have been killed in controversial wars in Iraq and Afghanistan, while at home surveillance and security measures have polarized both the government and the American people.

A decade on, the wound that 9/11 left has still not fully healed, and, in many respects, has only grown deeper and more difficult to cure.